1. Field of the Invention
This invention relates to electroluminescent complexes of platinum(II). It also relates to electronic devices in which the active layer includes an electroluminescent Pt(II) complex.
2. Description of the Related Art
Organic electronic devices that emit light, such as light-emitting diodes that make up displays, are present in many different kinds of electronic equipment. In all such devices, an organic light-emitting layer is sandwiched between two electrical contact layers. At least one of the electrical contact layers is light-transmitting so that light can pass through the electrical contact layer. The organic layer emits light through the light-transmitting electrical contact layer upon application of electricity across the electrical contact layers.
It is well known to use organic electroluminescent compounds as the active component in light-emitting diodes. Simple organic molecules such as anthracene, thiadiazole derivatives, and coumarin derivatives are known to show electroluminescence. Semiconductive conjugated polymers have also been used as electroluminescent components, as has been disclosed in, for example, Friend et al., U.S. Pat. No. 5,247,190, Heeger et al., U.S. Pat. No. 5,408,109, and Nakano et al., Published European Patent Application 443 861. Complexes of 8-hydroxyquinolate with trivalent metal ions, particularly aluminum, have been extensively used as electroluminescent components, as has been disclosed in, for example, Tang et al., U.S. Pat. No. 5,552,678.
Electroluminescent devices with an light-emitting layer of polymer doped with organometallic complexes of platinum have been disclosed by Burrows and Thompson in published PCT application WO 00/57676. Electroluminescent complexes of platinum and electronic devices made with them have been disclosed by LeCloux et al. in published PCT application WO 03/040257.
However, there is a continuing need for efficient electroluminescent compounds.